1. Field of the Invention
The present invention generally relates to a vibrating gyroscope and an electronic device using the same. More particularly, the present invention relates to a vibrating gyroscope for use in electronic devices such as video cameras having an anti-shake function, car navigation systems, and pointing devices, and to an electronic device using the same.
2. Description of the Related Art
FIG. 13 is a block diagram of a conventional vibrating gyroscope 50. The basic concept of the vibrating gyroscope 50 shown in FIG. 13 is disclosed in Japanese Unexamined Patent Application Publication No. 4-215017.
Referring to FIG. 13, the vibrating gyroscope 50 includes a vibrator 100, a sensor circuit 200, a driving circuit 300, a signal processing circuit 400, and a diagnostic circuit 700.
The vibrator 100 includes a first piezoelectric substrate 101, and a second piezoelectric substrate 102. The first piezoelectric substrate 101 has a first sensor electrode 104 and a second sensor electrode 105 on one principal plane thereof, and is polarized in the thickness direction. The second piezoelectric substrate 102 has a driving electrode 106 on one principal plane thereof, and is polarized in the thickness direction. The other principal plane of the first piezoelectric substrate 101 and the other principal plane of the second piezoelectric substrate 102 are bonded via an intermediate electrode 103. The sensor circuit 200 includes a first charge amp 220, a second charge amp 221, and a differential circuit 210. The driving circuit 300 includes an adder circuit 310, an automatic gain control (AGC) circuit 320, and a phase correction circuit 330. The signal processing circuit 400 includes a detector circuit 410, a smoothing circuit 420, and an amplifier circuit 430.
In the vibrating gyroscope 50 having such a structure, the first and second sensor electrodes 104 and 105 of the vibrator 100 are connected to the first and second charge amps 220 and 221, respectively. Each of the first and second charge amps 220 and 221 is connected to the adder circuit 310 and the differential circuit 210. The adder circuit 310 is connected to the AGC circuit 320, and the AGC circuit 320 is connected to the phase correction circuit 330. The phase correction circuit 330 is then connected to the driving electrode 106, the detector circuit 410, and a diagnostic circuit 700. The differential circuit 210 is connected to the detector circuit 410 and the diagnostic circuit 700. The detector circuit 410 is connected to the smoothing circuit 420, and the smoothing circuit 420 is connected to the amplifier circuit 430.
In operation, by applying a driving voltage to the driving electrode 106, the vibrator 100 undergoes flexural vibration in the thickness direction with the longitudinal ends free. When an angular velocity whose axis extends in the longitudinal direction is applied to the vibrator 100, the Coriolis force causes a bending displacement in the width direction. Hence, signals having the same phase, which are caused by the driving voltage, and charges having different phases are generated at the first and second sensor electrodes 104 and 105 according to the Coriolis force.
The first charge amp 220 converts the charge generated at the first sensor electrode 104 into a voltage, which is then input to the differential circuit 210 and the adder circuit 310. The second charge amp 221 converts the charge generated at the second sensor electrode 105 into a voltage, which is then input to the differential circuit 210 and the adder circuit 310. The adder circuit 310 adds the input signals so that the action of the Coriolis force maybe eliminated from the signals, and outputs the resulting signal to the AGC circuit 320. The AGC circuit 320 amplifies the received signal to provide a fixed amplitude, and inputs the result to the phase correction circuit 330. The phase correction circuit 330 corrects the phase of the input signal before inputting the driving voltage to the driving electrode 106 and the detector circuit 410.
The differential circuit 210 subtracts the input signals so that the signal corresponding to the driving signal may be removed from the signals, and inputs the signal corresponding to the Coriolis force to the detector circuit 410. The detector circuit 410 detects the input signal from the differential circuit 210 in synchronization with the driving voltage, and inputs the result to the smoothing circuit 420. The smoothing circuit 420 smoothes the input signal, and inputs it to the amplifier circuit 430, and the amplifier circuit 430 direct-current amplifies the input signal to output a signal corresponding to the angular velocity to the outside.
Since the sensor circuit 200 and the driving circuit 300 are connected to the diagnostic circuit 700 in the vibrating gyroscope 50, it can be determined whether or not both the sensor circuit 200 and the driving circuit 300 are functioning normally, or whether or not at least one of the sensor circuit 200 and the driving circuit 300 is functioning abnormally.
The conventional vibrating gyroscope 50 includes the diagnostic circuit 700 which is connected to the sensor circuit 200 and the driving circuit 300, and it is possible to determine whether or not the sensor circuit 200 and/or the driving circuit 300 are functioning normally.
Phenomena which arises as a result of abnormality of the differential circuit 210 and the phase correction circuit 330 can also be determined. For example, it can be determined whether or not there are defects such as breakage, degradation, and connection failure in the first sensor electrode 104, the second sensor electrode 105, and the driving electrode 106 of the vibrator 100, or whether or not a power supply line leading to the driving circuit 300 has been disconnected.
In the conventional vibrating gyroscope 50, however, only a part of the circuit components that can operate abnormally is monitored, and all abnormalities of the vibrating gyroscope 50 are not determined. In technologies such as vehicle-related technologies, since a variety of components interact with one another to establish a complex system, a small abnormality of one component may lead to fatal damage of the overall system. Therefore, it is desired that the presence of an abnormality of not only a part of a circuit but also all circuit components including a power supply be reliably determined.
However, since the diagnostic circuit 700 is not connected to the signal processing circuit 400 in the conventional vibrating gyroscope 50, abnormality of the signal processing circuit 400 cannot be examined. Thus, a problem occurs in that an incorrect angular velocity which is output due to an abnormality of the signal processing circuit 400 would not be recognized. Furthermore, since the vibrating gyroscope 50 does not allow abnormalities of a power supply to be examined, another problem occurs in that phenomena which do not arise as a result of abnormalities of the differential circuit 210 and the phase correction circuit 330, namely, variance in voltage values of the power supply, and incorrect angular velocity which is output due to failure such as noise or instantaneous stop of operation, would not be recognized.
Accordingly, it is an object of the present invention to provide a vibrating gyroscope capable of reliably examining abnormalities if some circuit components are not functioning normally.
It is another object of the present invention to provide a vibrating gyroscope capable of reliably examining abnormalities if a power supply is not functioning normally.
It is still another object of the present invention to provide an electronic device having a reliable system implemented in a vibrating gyroscope capable of reliably examining abnormalities.
To this end, in one aspect of the present invention, a vibrating gyroscope includes a vibrator having a driving electrode and a sensor electrode, a driving circuit for applying a driving voltage to the driving electrode, a sensor circuit which receives, from the sensor electrode, a signal corresponding to a bending displacement of the vibrator, a signal processing circuit for processing a signal input from the sensor circuit to sense an angular velocity, and a diagnostic circuit for examining whether or not the sensor circuit, the driving circuit, and the signal processing circuit are all functioning normally.
Preferably, the signal processing circuit includes a switching device and a detector circuit. The switching device outputs to the detector circuit either a signal input from the sensor circuit or a signal input from the driving circuit. The detector circuit detects a signal input from the switching device in synchronization with the driving voltage. In response to an input of the signal from the sensor circuit through the switching device, the signal processing circuit may sense an angular velocity. In response to an input of the signal from the driving circuit through the switching device, the signal processing circuit may output the signal indicating whether or not the signal processing circuit has an abnormality.
The diagnostic circuit may include a first determination unit for comparing an input power supply voltage with a reference voltage to determine whether or not the power supply voltage falls within a predetermined range.
The diagnostic circuit may further include a first rectifier circuit for rectifying a signal input from the sensor circuit, a second rectifier circuit for rectifying a signal input from the driving circuit, an adder circuit for adding the signal rectified by the first rectifier circuit and the signal rectified by the second rectifier circuit, and a second determination unit for determining whether or not the resultant signal from the adder circuit falls within a predetermined range.
In another aspect of the present invention, an electronic device includes a vibrating gyroscope having any of the foregoing structures.
Therefore, the vibrating gyroscope has the ability to examine whether or not all of the circuits as well as the power supply have an abnormality, thus providing a reliable examination of abnormalities if some of the circuit components or the power supply is not functioning normally.
Furthermore, the vibrating gyroscope allows the presence of abnormalities to be determined after the sensor circuit output signal and the driving circuit output signal are added, making it possible to reduce the number of comparators used therein, thereby providing simplification of circuitry.
The vibrating gyroscope includes a switching device, and has a structure such that the presence of abnormalities is checked only when an examination of abnormalities is required, thereby providing simplification of circuitry.
An electronic device according to the present invention includes a vibrating gyroscope capable of reliably detecting abnormalities, thereby providing a system required for desired reliability.